OSTEOLOGY OF POLYGLYPHANODON-—GILMORE: 249 
near its proximal end by a longitudinal groove that extends outward 
for a third of its length. The second ribs are slenderer than the first, 
and their outer ends are expanded, with the anterior edges abutting the 
posterior border of the first ribs and thus enclosing ovate sacral foram- 
ina. Viewed laterally, the ends of the ribs form the periphery of a 
half circle, thus forming a deep cavity between them that is open on 
the dorsal side. 
Measurement of the sacrals of the type (U.S.N.M. No. 15477) (in millimeters) 
Grearest leno thiol the .twO) CONthas 2 —— aes a ee ee eee 33 
Greatest width from tip to tip of the first sacral rib_-______-___--______--_-_-- 62 
Greatest! heichtt over! allvofsacral twos) eee ee a eee eee eee 23 
Caudal vertebrae.—The tail of Polyglyphanodon is represented by 
two articulated series of caudals and a few scattered vertebrae. Speci- 
men U.S.N.M. No. 15817, which has the best-preserved section of the 
Ficure 26.—Dorsal, sacral, and caudal vertebrae of Polyglyphanodon sternbergi Gilmore, 
U.S.N.M. No. 15477, type, ventral view, natural size: C, First caudal vertebra; D, dorsal 
vertebrae; R, last thoracic rib; S, sacral vertebrae. 
tail, consists of 1814 vertebrae that are in articulation with the sacrum, 
with parts of four others slightly separated from the last one of the 
series, as shown in plate 25. Specimen U.S.N.M. No. 15568 has an 
anterior caudal series of 22 vertebrae. A study of these two series 
seems to show that six anterior caudals are missing from U.S.N.M. 
No. 15568, so that we have knowledge of the first 28 vertebrae of the 
tail. The distal portion is missing in all specimens now available. In 
the restoration, plate 26, the missing portion of the tail has been 
restored after the 7guana, which Polyglyphanodon appears to resemble 
in many respects. 
The first caudal vertebra has a centrum that is subequal in length 
with the last sacral and retains the depressed cup and ball of the pre- 
socral region. The centra, beginning with the second, gradually in- 
crease in length posteriorly, but whether this lengthening continues 
into the distal portion of the tail cannot be determined from avail- 
able materials. The first caudal has long, flattened transverse proc- 
esses that extend outward horizontally from the sides of the centrum 
